This has been discussed about 20 times but there are vents under the front seats for the back. There is a photo in one of the original press releases and I can verify there are definitely vents aimed towards the back directly under the seats.

Yup, pretty much just like the X3. The differences in ducting between them is minimal. Given that, and the smaller cabin volume of the X1, I would think the rear passenger comfort would be better in the X1.